The present invention relates to a water dispersible agrochemical gel formulation.
Gels comprising a surfactant, an agrochemical, an acrylic acid polymer or copolymer and water are disclosed in W092/01377.
The present invention provides a water dispersible gel comprising (a) an effective amount of an ionic, water soluble agrochemical, (b) an effective amount of a crosslinked polyacrylic acid, (c) water, and (d) an amount of a base sufficient to cause a mixture of (a), (b) and (c) to gel.
The water dispersible gels of the present invention are suitable for packaging in standard containers or for containment in a water-soluble or water dispersible bag. The gels of the present invention are able to be dispersed in water, and the rate of dispersion depends on the degree agitation the gel water mixture is subjected to and also the amount of water present.
The ionic, water soluble agrochemical, is, for example, a herbicide (such as a paraquat salt (for example paraquat dichloride or paraquat bis(methylsulphate), a diquat salt (for example diquat dibromide or diquat alginate) or glyphosate or a salt or ester thereof (such as glyphosate isopropylammonium, glyphosate sesquisodium or glyphosate trimesium (also known as sulfosate)), an insecticide or a fungicide. It is preferred that the ionic, water soluble agrochemical is paraquat dichloride, diquat dibromide, glyphosate isopropylammonium or glyphosate trimesium (also known as sulfosate).
Crosslinked polyacrylic acids preferably have a molecular weight in the range 5xc3x97105 to 5xc3x97106, especially in the range 1xc3x97106 to 4xc3x97106. They are available commercially, for example as CARBOPOLs marketed by B F Goodrich (such as CARBOPOLs 5984, 2984, 940, 5984, 910, 941, 934, 934P or ETD 2050).
Suitable bases include ammonium or alkali metal (such as sodium or potassium) hydroxides, carbonates or bicarbonates (for example sodium hydroxide, sodium carbonate or sodium bicarbonate); or amines of formula R1R2R3N (wherein R1, R2 and R3 are, independently, hydrogen or C1-6 alkyl [optionally substituted by C1-6 alkoxy, hydroxy, halogen, C1-6 haloalkoxy (such as OCF3), C1-6 hydroxyalkexy (such as HOCH2CH2O) or C1-4 alkoxy(C1-6)alkoxy (such as CH3O (CH2)2O or CH3O(CH2) 5O] such as HOCH2CH2). It is preferred that R1, R2 and R3 are, independently, C1-6 alkyl or C1-6 alkyl monosubstituted with hydroxy. An amine of formula R1R2R3N is, for example, triethylamine or triethanolamine.
Alkyl and the alkyl part of alkoxy groups are straight or branched chain and preferably contains from 1 to 4 carbon atoms. It is, for example, methyl, ethyl, n-propyl, iso-propyl, n-butyl or tert-butyl.
In one aspect the present invention provides a water dispersible gel comprising (a) 1-60% (especially 5-60%) by weight of an ionic, water soluble agrochemical, (b) 1-4% by weight of a crosslinked polyacrylic acid, (c) 30-80% by weight of water, and (d) 2-20% by weight of a base.
In another aspect the present invention provides a water dispersible gel comprising (a) 20-60% by weight of an ionic, water soluble agrochemical, (b) 1-4% by weight of a crosslinked polyacrylic acid, (c) 30-80% by weight of water, and (d) 2-20% by weight of a base.
In a further aspect the present invention provides a water dispersible gel comprising (a) 20-60% by weight of an ionic, water soluble agrochemical, (b) 1-4% by weight of a crosslinked polyacrylic acid, (c) 30-80% by weight of water, (d) 2-20% by weight of a base, and (e) 1-40% of an electrolyte.
When a gel of the present invention is going to be held in a water-soluble or water dispersible sachet and when the ionic strength of said gel is low it is preferred that said gel comprises a suitable electrolyte in addition to the ionic agrochemical present. The electrolyte helps to improve the insolubility of the material from which the sachet is made in the gel. (See Polyvinyl Alcoholxe2x80x94Properties and Applications pages 38-43, edited by C. A. Finch, published by J Wiley and Sons in 1973 and EP-A1-0518689.) Suitable electrolytes may, for example, comprise a cation or mixtures of cations selected from the list comprising: ammonium, copper, iron, potassium and sodium; and an anion or mixture of anions selected from the list comprising: sulphate, nitrate, fluoride, chloride, bromide, iodide, acetate, tartrate, ammonium tartrate, benzenesulphonate, benzoate, bicarbonate, carbonate, bisulphate, bisulphite, sulphate, sulphite, borate, borotartrate, bromate, butyrate, chlorate, camphorate, chlorite, cinnamate, citrate, disilicate, dithionate, ethylsulphate, ferricyanide, ferrocyanide, fluorosilicate, formate, glycerophosphate, hydrogenphosphate, hydroxostannate, hypochlorite, hyponitrite, hypophosphite, iodate, isobutyrate, lactate, laurate, metaborate, metasilicate, methionate, methylsulphate, nitrite, oleate, orthophosphate, orthophosphite, orthosilicate, oxalate, perborate, perchlorate, phosphate, polyfluoride, polychloride, polyiodide, polybromide, polysulphide, polysulphate, polysulphite, salicylate, silicate, sorbate, stannate, stearate, succinate or valerate. Preferred electrolytes are ammonium sulphate, sodium sulphate, potassium sulphate, copper sulphate, ammonium nitrate, sodium nitrate, potassium nitrate, sodium chloride or potassium chloride.
It is preferred that sufficient base is added to cause the pH of the water dispersible gel to be in the range 6 to 10, especially 6 to 8. If too much base is added the pH of the mixture will be too high and the gel formed will break down. Thus, in another aspect the present invention provides a water dispersible gel comprising (a) an effective amount of an ionic, water soluble agrochemical, (b) an effective amount of a crosslinked polyacrylic acid, (c) water, and (d) an amount of a base sufficient to cause the pH of the resulting gel to lie in the range 6 to 10 (especially 6 to 8, particularly 6 to 7).
In a further aspect the present invention provides a water dispersible gel which comprises 2-5% by weight of an alkali metal hydroxide, carbonate or bicarbonate.
A Bohlin VOR rheometer may be used to measure the elasticity and viscosity of the gel formulation of the present invention under low shear conditions. Here a sinusoidally varying strain (at a frequency of 1 Hz) is applied to a sample of a formulation maintained at 25xc2x0 C. The resultant stress, which also varies sinusoidally with time, is observed. The ratio of the maximum stress to the maximum strain is known as the complex modulus (G*). By using the phase shift, xcex4, between the stress and strain wave forms the complex modulus may be split into two componentsxe2x80x94the storage (elastic) modulus (Gxe2x80x2) and the loss (viscous) modulus (Gxe2x80x3). The storage and loss moduli are a measure of the energy stored and the energy lost respectively, in an oscillatory cycle. The relative magnitude of the loss and storage moduli (Gxe2x80x3/Gxe2x80x2=Tan xcex4) provides information on the elasticity of the gel. The lower the value of Tan xcex4 the greater the degree of gelation. Similarly, gels are characterised by their non-Newtonian flow behaviour, exhibiting, for example, yield values and shear thinning. Yield values can be measured using a Haake Rotovisco RV20 under high shear conditions.
In a still further aspect the present invention provides a water dispersible gel as hereinbefore described having a storage modulus (Gxe2x80x2) in the range 1-1000 Pa, preferably 20-500 Pa, more preferably in the range 100-200 Pa.
In another aspect the present invention provides a water dispersible gel as hereinbefore described having a tan xcex4 (ratio of loss modulus to storage modulus) of less than 1, preferably less than 0.5, more preferably less than 0.2, especially less than 0.1. (Rheological measurements are carried out at a temperature of 25xc2x0 C. Oscillation measurements are carried out within the linear viscoelastic region as determined by strain sweep measurements made at a frequency of 1 Hz (6.28 rad/s)).
In another aspect the present invention provides a water dispersible gel comprising 10-20% by weight of a base of formula R1R2R3N (wherein R1, R2 and R3 are as defined above).
In another aspect the present invention provides a water dispersible gel comprising 1.5 to 3, especially 2 to 2.75 by weight of a crosslinked polyacrylic acid.
When the gel of the invention is to be contained in a water soluble or water dispersible sachet it is preferred that a plasticiser is included in the gel. The plasticiser is preferably present in the range 0.1 to 1% (especially 0.3 to 0.75%) by weight. Suitable plasticisers include glycols (for example ethylene glycol), glycerine and dibutylphthalate.
Depending on the nature of the ionic, water soluble agrochemical present, one or more adjuvants or co-formulants (such as a wetter or anti-freezing agent) may also be comprised in the gel of the present invention. Adjuvants include a neutral or anionic surfactant [such as a soap, a salt of an aliphatic monoester of sulphuric acid (for example, sodium lauryl sulphate), a salt of a sulphonated aromatic compound (for example, sodium dodecylbenzenesulphonate, an alkyl glucoside or a poiysaccharide].
In a further aspect the present invention provides a gel of the present invention as defined above which also comprises a chelating or sequestering agent for calcium ions. A suitable chelating or sequestering agent is ethylenediaminetetraacetic acid.
Over and above the components already mentioned, a water dispersible gel of the present invention may also comprise an adhesive, an antifoaming agent, a buffer, a deodorant, a dye, an emetic, a preservative, an odourant, a perfume, a safener, a further solvent, a stabiliser, a synergist, a thickener or a wetting agent.
A gel of the invention can be made simply by initially mixing all the components other than the base, and then adding the base to form the gel. Thus it can be appreciated that a gel of the present invention is made by a pH switching process.
In a further aspect the present invention provides a containerisation system comprising a water soluble or water dispersible bag containing a water dispersible gel of the present invention, provided the gel has sufficient ionic strength.
The water soluble or water dispersible bag can be made from a variety of materials and preferred materials are polyethylene oxide, methyl cellulose or, especially, polyvinylalcohol (PVA). The PVA is generally partially or fully alcoholysed or hydrolysed, for example 40-100%, especially 80-100%, alcoholysed or hydrolysed polyvinyl-acetate film. It is preferred that the PVA film is a laminate of two or more thicknesses of film, a surface modified film or a co-extruded film (such as is described in WO 94/29188).
In another aspect the containerisation system comprises a bag-in-bag arrangement comprising a water-soluble or water dispersible bag holding a gel of the present invention and a second water-soluble or water dispersible bag also holding a gel of the present invention. This bag-in-bag arrangement can be used, for example, to contain a gel of the present invention comprising an ionic, water soluble agrochemical in the inner bag and a gel of the present invention comprising adjuvant, synergist or penetrating agent in the outer bag.
In a further aspect the containerisation system provides two water-soluble or water dispersible bags joined at a common seal, one containing a gel of the present invention comprising one ionic, water soluble agrochemical, the other bag containing a gel of the present invention comprising a different ionic, water soluble agrochemical.
In a still further aspect the containerisation system comprises a bag-in-bag arrangement comprising a first water-soluble or water dispersible bag holding a gel of the present invention and a second water-soluble or water dispersible bag surrounding the first water-soluble or water dispersible bag. The advantage of this system is that the second bag presents a barrier to any matter leaking from the first bag.
In another aspect the containerisation system comprises a bag-in-bag arrangement comprising a first water-soluble or water dispersible bag holding a gel of the present invention and a second water-soluble or water dispersible bag holding an agrochemical composition (such as a liquid, granule, powder or gel composition comprising a fungicide, herbicide, insecticide, adjuvant, synergist or penetrating agent).
In a further aspect the containerisation system comprises a bag-in-bag arrangement comprising a first water-soluble or water dispersible bag holding an agrochemical composition (such as a liquid, granule, powder or gel composition comprising a fungicide, herbicide, insecticide, adjuvant, synergist or penetrating agent) and a second water-soluble or water dispersible bag holding a gel of the present invention.
In another aspect the containerisation system provides two water-soluble or water dispersible bags joined at a common seal, one containing a gel of the present invention comprising a fungicide, herbicide, insecticide, adjuvant, synergist or penetrating agent the other bag containing an agrochemical composition (such as a liquid, granule, powder or gel composition comprising a fungicide, herbicide, insecticide, adjuvant, synergist or penetrating agent).
The water soluble or water dispersible sachet can be formed and filled using standard techniques (such as thermoforming or vertical form-fill-sealing).
In use the containerisation system can be mixed with water to give a sprayable solution or dispersion of the ionic chemical. The containerisation system is especially useful in agriculture.